1. Field of the Invention
This invention generally relates to cellular PDA devices, and more specifically, to cellular PDA devices having both a data modem and a cellular phone capability.
2. Background Art
The PDA, or personal digital assistant, is a general-purpose computing machine sized and shaped generally to fit into the hand of a user or to be placed in a pocket, and allows a user to run various applications including personal information management applications such as address books and daily organizers. Many PDAs offer Internet connectivity capabilities and include a data modem that can be used to manage instantly many kinds of information, from e-mail, to medical data, to stock reports. Recently, PDAs have been developed that also have a cellular phone capability.
When using some Web or Web based technologies, these PDAs need to open the modem and leave a connection for the entire period of the data session. They need to maintain their connection for data functions such as enterprise messaging and push type application functionality where the back-end server sends data to the PDA device. This significantly drains the battery of these devices while they maintain their connection. Typically, these devices save battery life by causing the modem to enter a dormant stage when no data is being transmitted. This, however, prevents back-end servers from delivering data to the client device in common protocols that are used for such communication. There is a tradeoff between application functionality and battery life.